A well known type of hermetically sealed rotary compressor for refrigeration systems comprises a hermetic casing containing a compressor consisting of a cylindrical wall member and end plates defining a compression chamber, a roller eccentrically mounted within the chamber and a vane slidably mounted within a vane slot provided in the cylinder wall. The inner radial edge of the vane engages the periphery of the rotor to divide the chamber into a high pressure side and a low pressure side. The vane is biased against the roller by a spring. In the operation of such a compressor, rotation of the roller draws gas into the low pressure side and discharges the compressed gas through a discharge port communicating with the high pressure side. The discharge port is valved to the interior of the casing, which accordingly, during compressor operation is maintained at the relatively high discharge pressure. The high pressure gas in the casing acting on the outer radial end of the vane assists the spring in maintaining the inner radial end of the vane against the roller during compressor operation. During the operation of a compressor of this type, there is a considerable side force exerted on the vane or, more specifically, the portion thereof extending into the compression chamber, due to the fact that one side or face of the vane is exposed to high or discharge pressure and the other to low or suction pressure. This side force exerted on the vane portion extending into the compression chamber causes a friction force which inhibits the motion of the vane in the slot. This frictional force is sufficient that it will prevent the vane from following the roller to bottom dead center during compressor start up when the pressure in the case is not high enough to assist the spring in overcoming the frictional forces and maintaining the vane against the roller. Accordingly, it is possible during compressor start up for the vane to separate from the roller and not be in continuous contact as the roller moves from top to bottom dead center position. When the vane does separate from the roller continued rotation of the roller from the bottom to top dead center will cause it to strike the vane, thereby creating an objectionable noise. This frictional force on the vane is critical only during start up of the compressor since once the hermetic case reaches operating conditions the pressure in the case acting on the outer end of the vane is sufficient together with the spring to overcome the frictional forces and maintain the vane against the roller through the continuous rotation of the roller. The result of the frictional forces is a noise which is present only during compressor start up.